ABSTRACT
The electrochemical-mechanical degradation of ultrahigh Ni cathode for lithium-ion batteries is a crucial aspect that limits the cycle life and safety of devices. Herein, the study reports a facile strategy involving rational design of primary grain crystallographic orientation within polycrystalline cathode, which well enhanced its electro-mechanical strength and Li+ transfer kinetics. Ex situ and in situ experiments/simulations including cross-sectional particle electron backscatter diffraction (EBSD), single-particle micro-compression, thermogravimetric analysis combined with mass spectrometry (TGA-MS), and finite element modeling reveal that, the primary-grain-alignment strategy effectively mitigates the particle pulverization, lattice oxygen release thereby enhances battery cycle life and safety. Besides the preexisting doping and coating methodologies to improve the stability of Ni-rich cathode, the primary-grain-alignment strategy, with no foreign elements or heterophase layers, is unprecedently proposed here. The results shed new light on the study of electrochemical-mechanical strain alleviation for electrode materials.
ABSTRACT
Natural photosynthesis involves a subtle electron transfer mechanism in which freely-moving electron transfer intermediates (plastoquinone and plastocyanin) are capable of effectively separating the photo-generated carriers, and therefore, it has high quantum efficiency. Inspired by this mechanism, in this study, carbonate (CO32-) ions were employed as hole vehicles to promote photo-generated carrier separation, and greatly improved the photocatalytic hydrogen evolution activity of K4Nb6O17 nanosheets. The hydrogen evolution rate at the optimal concentration of CO32- ions reached 2018 µmol h-1 g-1, which was 16.3 times that of the blank sample (124 µmol h-1 g-1). This marked enhancement was based on the transfer of holes from the photocatalyst to the sacrificial reagent (methanol) via CO32- ions; this process is faster than direct hole transfer between the photocatalyst and sacrificial reagent. This bio-inspired strategy provides a facile and cost-effective approach to improve the solar-to-fuel conversion efficiency of photocatalysts.
ABSTRACT
As environmental and energy problems have worsened worldwide, research for developing renewable energy has become urgent. Presently, the primary focus of such research is directed towards the photocatalytic decomposition of water to produce hydrogen as an energy source. Herein, ZnO nanosheet/CdS nanoparticle heterostructures were synthesized by a mild wet chemical reaction and displayed a high photocatalytic efficiency (1040 µmol g-1 h-1) without Pt loading under visible light radiation. The structure was prepared by first constructing two-dimensional nanocrystalline ZnO flowers and then loading CdS nanoparticles onto the nanocrystals. Results show that this structure can facilitate the separation of photogenerated electrons and holes and improve the photocatalytic efficiency and stability of the materials in the photocatalytic decomposition of water. By changing different experimental conditions to prepare a variety of samples and test their properties, we can analyze the optimal parameters for the preparation of this material.
